Throat plate



OCt'l3, 1959 R w, wgN 2,908,237

- THROAT PLATE Filed Feb; 21, 1957' IFIG.6.

INVENTOR. RAG/v42 a4 W/A/Bk United States Patent The present invention relates-tothe manufacture of an and adjacent to the needle hole.

2,908,237 Patented Oct; 13, 1959 r ce hole achannelway extending adjacent and rearw'ardlyof; the needle hole... A lead-in wire and contact means lie within thechannelway and are. bonded therein in insulated relation to the main. body of the throat plate withzther contact means lying substantially rearwardly of Advantage'ously,; a

thread guideway is provided. rearwardly of. the needle hole' and along the line where the stitching. normally passes, with. the contact means extending along and bounding one side of the thread guideway and with. the plate proper extending. along and bounding. the other side of the thread. guideway. The thread guideway is improved throat plate for sewing; machines, and imparticular. to athroat plate which is constructed tO-SGFVG as a circuit completing element in: a bobbin runoutcdetection system.

. My U.S. Patent No; 2,854,938 of 0ctober 7, 1958 is concerned with: the problem. of providing a visual: warning or control function-when the supply of bobbin or bottom thread in a. sewingtmachine. is about. to become exhausted. The purposeyof obtaining this warning or control functionis to apprise the operator that the bobbin must be replaced or to'achieve' an, automatic shutdown of the machine. I 2,854,938- of October 7,. 1 958, lz haye found that. the electrical conductivity state or condition of the bobbin thread may be changed from. itsnormal state alonga section adjacent to and spaced fromthe-innermost end dimensioned so that the electrically conductive region, although exceptionally short. in length and comparable inqsection'to the normal cross-section of the thread, will bridgethe-width of the guideway and complete the electrical connection of the contact means to the plate proper which energizes the associated warningor controlcircuit.

In accordance with-method aspectsof the present inyention, 'a conventional throat, plate of the type usually employed in a sewing-machine may be modified for use as. part ofmy improved bobbin runout detection system As detailed inmy U.S. PatentNo.

by formingachannelway in. the throat plate having a section extending. adjacent. the needle hole, electrically assembIingalead-in or terminalwire and a contact membenplacingthe assembly of. the wire and the'contact rn'ernberdn: the channelway with the contact. member {rearwardly ofthe needle and. with the assembly insulated from the throat plate, and bounding, the assembly in the channelwayso that for all intents and purposes the asfsembly is an integral part of the throat plate. To adof the wound bobbin; Upon feeding of this section, of

changed electrical conductivity to or. through. the sewing mechanisms, the change in electrical conductivity may be sensed and employed to initiate the warning or control function. In an illustrative embodiment according to my previous invention, a bobbin isprovided which .is of comparatively non-conductive thread and tis wound on the conventional bobbin spoolor ina. coreless form with asection or length of the bobbin thread adjacent to and spaced from its innermost endtreated. with-electrical'powder to provide conductive surfaces. of low electrical resistivityand. high'electncalconductivity. During the normal operation of the sewing machine, the wound bobbin delivers thread which is of; the usual low con.- ductivity until such times as the section or length of vantage, a throat plate constructed substantially. in ac cordance with mymethod' is not structurally weakened andLthe presence of the isolated contact member and the terminal" wire does not interfere with its normal construction which enables its use with the conventional feed dog and presser foot of the sewing machine.

Q .The' above brief description, as well as further. objects, Ifeatur'e's and advantages of the present invention will be bestappreciated by reference to the following detailed description of a presently preferred;.but illustrative emhigh conductivity is pulled from: the bobbin. and advauced through the stitching mechanisms. This high conductivity section, which. may be made exceptionally short in length, is employed. tophysically complete an electrical circuit, which circuit. stays. energized. until the sensing or detecting mechanism is reset bytheoperator.

The circuit was completed in accordance with-the teachings of my patent by isolating, the'segment ofthe throat plate surrounding the needle hole from the remainder of the machine and. relying upon? the electrically conductive section coming through the needle hole andbridging the isolated" segment to a contiguous.portionsofv the machine whereby the circuit was activated 'for achieving the warning or control function.

It is an object of this invention. to-provide an improved throat plate for use ina-bobbin runout detection system of the aforesaid. character. Specifically, it is'within the contemplation of the present invention. to previde an improvedthroat plate constructed toallowfor. the completion of the control circuit. for the runout detection 'bodiment and the details of a typical method of assembly, when taken in: conjunction with the accompanying drawings, wherein Fig; l is a; perspective' view, partiallyexploded, showing the component parts of an improved throat plate in accordance with the present invention; i

Fig. 2 is a pl'anview, on an enlarged scale and partially broken away, showing a completed throat plate embodying features of the-present invention;

a Fig; 3"-is' a sectional view on an enlarged scale taken substantially along the line -33l of Fig. 1 and showing 7 a first step in the assembly of a terminal or lead-in wire system in response toan-exceptionally smalh or short throat plate comprises a mainbody having aneedle withthe throat plate in accordance with the present invention;

' Fig. 4" is. a view similar to Fig. 3 but showing the insulated Iead in or terminal wire as assembled with the throat plate;.

a a Fig. 5': is a showing similar to Fig- 4' after the excess material above the top face of the throat'plate and a portion of the lead-in wire are removed, said view being taken substantially alongthe line 5-5 of. Fig.1 2'; and

Eigzfi is' a sectional View taken substantially along the line of Fig. 2, a thread being shown in cross section. lying. within the thread guideway rearwardly of the needleahole.

' Referring. now specifically to the drawings, there is shown in Fig.1 1; the component parts of an improved throat plate 1.03maccordance with the present invention which includes a main body or plate part 12, a lead-in wire/.14, contact-member, a terminal plug 18 and a connecting wire 20.

V. I. The main body or throat plate proper 12 is essentially of conventional construction and includes a needle hole 22, a number of feed slots 24 and countersunk holes 26. The. needle hole 22 permits theneedle 'of the sewing ma chine to extend through-the throat plate 10..for:co-action with the hook'and bobbin mechanisms; the feed slots 24 permit the, work-contacting surfaces of the four-motion feed dog. of the machine to engage the under-surface of the workandfto: advance the same .past the needle; and the holes 26enable .themounting of the throat plate on the sewing machine as part of the feed b'ed thereof. 7

In accordance with the present'invention, the throat plate is modified to incorporate a channelway 30 or slot which extends rearwardly from the needle hole '22 at'a. location offset to one side of the needle hole and spaced from and parallel to the line L, along which the stitching or seam moves' during normal operation of the sewing machine. channelway 30 is dovetailed in cross section for a purpose to be; subsequently described. ;At its rearward end, the channelway 30 is in communication with a terminal opening 32 which receives the insulating terminal plug 18 in a manner to be subsequently described. At its forward end the channelway or slot 30 is in communication with a laterally-extendnig cut out 34 which has one side contig uous with the outer side of the channelway '30'and As seen best in Figs. 3 to 5, inclusive, the

' guideway.

has its other side extending to and terminating substan- U I tially along the stitch line L and ate location in alignment with and rearwardly of the needle hole 22. The disposition .of the channelway and the cutout 34 is such as not to interfere with the required slots 24 for th feed dog. However, in some installations, it will be necessary the small cutout 34 do not interfere with providing the to modify the feed dog by cutting away portions thereof.

required clearance for the work-engaging surfaces of the feed dog to come into contact with the under surface of the assembly to be stitched. a

The'co'ntactmember 16 is mountedon the forward terminal portion 14a of the terminal. or lead-int'wire through the provision of a welded or soldered joint 36 (see 'Fig. 6). The terminal portion 14a of thewire 14 rna'yextend for substantially along the entire adjacent side of the contact member 16 to assureadequate electrical connection between the wire and the contact meniberand to provide the requisite mechanically rigid assembly between the wire and the contactmember. The contact member 16, which is inthe form .of an insert or inlay for the throat plate, may be fabricated of any electrically conductive material, but preferably isof the same material as the throat plate proper.

The insulating plug or terminal 18 may be a molded piece of ceramic or may be'of plastic. It has been found convenient to employ a plug made of Zytel'to surround the rear end portion of the lead-in wire 14 to which rear terminal plug'18 is either force fitted extends laterally in front of the lead-in wire 14 which is connected at the side of 16a thereof. At its opposite side 16b the contact member 16 terminates substantially along the line to be ultimately occupied by the thread T. Althrough a single strand of thread is shown in Fig. 6, it will be appreciated that this thread is part of a stitched assembly and diagrammatically represents the bobbin thread which is part of the stitched assembly, the remaining portions of the stitched assembly and the top thread being deleted for the purpose of illustration.

V A thread guideway 40 is provided along the stitch line L rearwardly of the needle and is bounded at one side by the adjacent side 16b of the contact member 16 and at the other side by the'plate proper. Extending between the needle hole and the adjacent end of the thread guide- Way 40 is a small chute, designated generally by reference numeral 42, which has a chamfered base extending upwardly from its forward end which 'isdisposed below theitop face 12a-of the plate 12 and terminates in the guideway. I The chute has somewhat convergent side walls 42a; 42b which merge into the adjacent sides of the thread Referencewill how be made in sequence to Figs. 3 to 5', inclusive, for a detailed description of the present method of modifying a conventional throat plate for use as part of my run-out detection system. a I Initially the throat plate 12 is formed with the channelwayf-30, 'theterminal opening 32 and the cutout 34 as detailed in conjunction with Fig. l. Thereupon, a first quantity 38a of a suitable bonding resin is placedin' the channelway-SG and the terminal or lead-in wire-14 is wrapped in a partial sheath of insulating paper 44. A second quantity 38b of bonding resin is filled in about the wireand within the partial sheath 44. Thereupon the assembly of the Wire 14 and the sheath 44 is placed within the channelway 30 (see Fig. 4) with the wire 14 insulated from the throat plate 12 by. the resinous mass 38a, 38b and the paper sheath or separator 44. In a similar fashion the'contact member 16 which is slightly undersized in relation to the cutout 34 is placed within the cutout and insulated therefrom by the application therebetweeri" of the bonding resin and a sheath. The into the opening 32-or bonded therein by an adhesive. A suitable bonding resin which'has beenfound to be particularly useful inaccordance withthe present invention is an epoxy resin in liquid form which is cured with an appropriate epoxy hardener. Such epoxy resins are available in the end portion is electrically joined the connecting wire 20. r

This connectingwire is connected to an energization coil of a relay or to a microswitch or any other: control element of the sensing or control circuit. A typical circuit used in accordance with the present invention is detailed in my said patent. 7 Reference will now be made to'Figs. 2 and 6 for adescription of the completed throat plate in accordance with the present invention. As seen in Fig. 2, the contact member 16 disposed in the cutout 34 and the terminal or leadin wire 14 lies within the channelw'ay or slot 30, the assembly of said channel contact member .16 and the lead-in. wire 14 being insulated from the plate proper by the provision'of insulating material, generally designated by the reference numeral 38. The terminal plug 18 ex-- tendsthrough the terminal opening 32 and serves to inbest in conjunction with Fig. 6, thecontact member 16 market'under the Bakelite trademark and are identified as epoxy resin ERL-2795 and epoxy hardener ERL-2807. Suitable formulations are four to five parts of'the epoxy resin to one part of the epoxy hardener. Once the epoxy resin -is cured, the same provides an integral bond which fixesthe wire 14 and the contact member 16 in the chan- -nelway' and cutout. The dovetail construction of the 'channelway-30, as seen in, Figs. 3 to 5, inclusive, assures that'th'e hardened resinous insert cannot readily pull out fromits confining slot. After the assembly illustrated in Fig. 4 hashardened, the uppermost face 12a of the throat plate 12 is sanded, for example by placing the 'sameface down on a sanding belt, to remove'the excess i hardened resin above the level of the face12a. Incident to such removal, portions of the sheath or paper separator 44 are sanded away; and as illustrated in Fig. 5, any portions of the wire 14 which project above the plane of the face 12a is chamfered off. When completed the wire 14 is adequately insulated from the throat plate 12 by a the paper separator 44 and the hardened resinous mass 38. 'As seen in Fig. 6, a similar paper wrap or separator 46 isem'ployedin conjunction with the inlay or insert 16 to assurethat' the' same will be electrically isolated from the bounding walls of the cutout B4. In some instances itmay be advantageous to makeithe cutout 34 of-inverted dovetail section so that if any'downward force aisexertedon the inlay during normal use, said force will not dislodge such contactjfrom'the-cutout 34. Insome instances it may not be necessary toemploy the paper separators or sheaths 44, 45 ineffecting the assembly; however, such sheaths are particularly useful clue to the comparatively small clearances between the wire and the contact member and the surrounding portions of the plate.

After the wire and the contact member are embedded within the plate/the guideway 40. is completed by milling a slot and as a part of this operation the guiding funnel 42 is formed intermediate the needle hole 22 and the thread guideway '40.

The conventional sewing machine is modified to' employ the present throat plateinconjunction with bobbin run-out detecting system of the type described in detail in my said patent. Such modification involves the attachment to the sewing machine of a sensing unit which is electrically connected to the wire 20, the use of the specially prepared bobbin with the electrically conductive section, and the replacement of the standard throat plate with the present improved throat plate. As the conductive portion of the thread comes up through the needle hole 22 during normal operation of the stitching mechanisms of the machine, such conductive portion is directed to the thread guideway 40 by the funneling channel 42. Upon entering such thread guideway the conductive portion effectively bridges the contact member 16 to the throat plate proper. This is effective in the control circuit to initiate the desired external function incident to the detection of runout of the bobbin thread. It will be appreciated that by proper dimensioning of the thread guideway 40, that is by having a guideway substantially of the width of the thread, a small electrically conductive portion on the thread will be sufficient to at least momentarily bridge the contact member 16 to the throat plate proper to connect these two electrical terminals together.

Experience indicates that the present improved throat plate is virtually as strong as the conventional throat plate and the presence of the insulated contact member 16 and lead-in wire 14 do not structurally weaken the throat plate or interfere with the operation of the feed dog or the needle of the sewing machine.

A latitude of modification, change and substitution is intended in the foregoing apparatus and method and accordingly the claims should be interpreted broadly and in a manner consistent with the spirit and scope of the disclosure. In some instances, some features of the invention will be used without a corresponding use of other features.

What I claim is: i

1. An improved throat plate for a sewing machine comprising a main body of electrically conductive material having a needle hole and a channelway extending adjacent said needle hole, a lead-in wire and contact means both of electrically conductive material lying within said channelway, and means in said channelway bonding said wire and contact means to said main body and insulating said wire and contact means from said main body.

2. An improved throat plate for a sewing machine comprising an electrically conductive main body having a needle hole and a cutout extending adjacent said needle hole, electrically conductive contact means lying within said cutout, and means in said cutout bonding said contact means to said main body with said contact means insulated from said main body.

3. An improved throat plate for a sewing machine comprising an electrically conductive main body having a needle hole and a cutout extending adjacent said needle hole, a lead-in wire having an electrically conductive contact part lying within said cutout, and means bonding said wire and contact part to said main body and insulating said wire and contact part from said main body.

4. An improved throat plate for use with a bobbin runout detection device comprising a main plate having a needlehole, said main plate being formed with a slot extending rearwardly from said needle hole at alocation spaced from and substantially parallel to a stitch line extending rearwardly of said needle hole and in alignment therewith, said main plate being formed with a cutout, said slot opening laterally at the end thereof adjacent said needle hole'into one side of said cutout, said cutout terminating at the other side thereof substantially along said stitch line, a lead-i'nwire disposed insaid slot, means mounting said wire insaid slot in insulated relation from said main plate, a contact member disposed'in said cutout and electrically connected" to said wire, and means mounting said contact member in insulated relation from said main-plate with said contact member having a-side extending substantially along said stitch line.

5. An improved throat plate for use with a bobbin runout detection device comprising a main plate having a needle hole, said main plate being formed with a slot extending rearwardly from said needle hole and at a location laterally spaced from a stitch line extending rearwardly of said needle hole andin alignment therewith, said main plate being formed with a cutout, said slot opening laterally at the end thereof adjacent said needle hole in said cutout, said cutout terminating substantially along said stitch line, a lead-in wire disposed in said slot, means mounting said wire in said slot in insulated relation from said main plate, a contact member disposed in said cutout and electrically connected to said wire, means mounting said contact member in insulated relation from said main plate with said contact member having a side extending substantially along said stitch line, said main plate being formed with a thread guideway along said stitch line and having at one side thereof said contact member.

6. An improved throat plate for use with a bobbin runout detection device comprising an electrically conductive main plate having a needle hole disposed along a stitch line extending rearwardly of said needle hole and in alignment therewith, said main plate being formed with a cutout at one side of said stitch line and terminating at one of its sides substantially along said stitch line, an electrically conductive contact member disposed in said cutout, and means mounting said contact member in insulated relation from said main plate with one side of said contact member extending substantially along said stitch line.

7. An improved throat plate for use with a bobbin runout detection device comprising an electrically conductive main plate having a needle hole disposed along a stitch line extending rearwardly of said needle hole and in alignment therewith, said main plate being formed with a cutout at one side of said stitch line and terminating at one of its sides substantially along said stitch line, an electrically conductive contact member disposed in said cutout, means mounting said contact member in insulated relation from said main plate with said contact member extending substantially along said stitch line, said main plate being formed with thread-guiding means extending along said stitch line and having said contact member bounding one side of said thread guiding means.

8. An improved throat plate for use with a bobbin runout detection device comprising an electrically conductive main plate having a needle hole disposed along a stitch path which extends rearwardly of said needle hole, said main plate being formed with a cutout at one side of said stitch path, said cutout terminating at a bounding edge extending substantially along said stitch path, an electrically conductive contact member disposed in said cutout, and insulating means mounting said contact member in insulated relation from said main plate, said contact member having one of its edges extending substantially along said stitch path, said one edge of said contact member being substantially coextensive with said bounding edge of said cutout and being separated therefromtby said insulating means whereby an electrical path may be completed between said main plate and said contact member when the coextensive edges are bridged by a conductive material. 1 I I 9. An improved throat plate for use with a bobbin runout detection device comprising an electrically conductive main plate having a needle hole disposed' along a stitch path which extends rearwardly of said needle hole, said main plate being formed with a cutout at one side of said'stitch path, said cutout terminating at a bounding edge extending substantially along said stitch path, an electrically conductive contact member disposed in said cutout, and insulating means mounting said contact member in insulated relation from said main plate; said contact member having one of its edges extending substantially along said stitch path, said one edge of said contact member being substantially coextensive with said bounding edge ofsaid cutout and being separated therefrom by said insulating means whereby an electrical path may be completed between said main plate andsaid contact member when the coextensive edgesiare bridged by a conductive material, and thread guiding means formed along said stitch path rearwardly of said needle hole.

I References Cited in the file of this patent UNITED STATES PATENTS Nachm'an Sept. 10, 1946 

